Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

Methods and systems are disclosed for using a common frequency spectrum
for simultaneous upstream and downstream communications in a network by
implementing directional diversity techniques. Non-reciprocal coupling
devices, such as circulators, may be configured in the network to provide
unidirectional transmission of each signal to prevent interference. In
some embodiments, feed-forward interference cancellation is utilized to
increase signal isolation of upstream and downstream signals.

Claims:

1. An apparatus comprising a network branch configured to simultaneously
transmit over a conductor, electromagnetic transmissions in opposite
directions modulated at the same frequency.

2. The apparatus of claim 1, further comprising a non-reciprocal coupling
circuit configured to: receive out-bound transmissions on a first port
and output the out-bound transmissions on a second port to the network
branch; receive in-bound transmissions on the second port from the
network branch and output the in-bound transmissions on a third port; and
isolate the out-bound transmissions from the third port.

3. The apparatus of claim 2, further comprising a circulator having three
ports electrically coupled to the first, second, third ports
respectively.

4. The apparatus of claim 2, further comprising a feed-forward
interference cancellation circuit configured to sample the out-bound
transmissions at the first port and output cancellation transmissions on
the third port.

5. The apparatus of claim 1, wherein the conductor is a coaxial cable.

6. The apparatus of claim 1, wherein the transmissions include analog
television signals traveling in a first direction and digital data
transmissions traveling in a second direction opposite the first
direction.

8. The apparatus of claim 1, wherein the apparatus is a communications
network configured to deliver television transmissions and data
communication transmissions over the conductor in opposite directions
modulated in the same frequency bandwidth simultaneously.

9. The apparatus of claim 8, wherein the television transmissions
includes one or more of analog television transmissions and digital
television transmissions.

10. The apparatus of claim 1, wherein the apparatus is a communications
network configured to deliver television transmissions and data
communication transmissions, wherein the data communication transmissions
include transmissions over the conductor in opposite directions modulated
in the same frequency bandwidth simultaneously.

11. A network gateway comprising: a network interface port; a content
transmission port; a data port; and a non-reciprocal signal distribution
circuit configured to: receive content signals modulated at a first
frequency on the network interface port and output the content signals on
the content transmission port; receive out-bound data service signals
modulated at the first frequency on the data port and output the
out-bound data service signals on the network interface port; and isolate
the out-bound data service signals received on the data port from the
content transmission port.

12. The network gateway of claim 11, wherein the non-reciprocal signal
distribution circuit is further configured to: receive in-bound data
service signals modulated at a second frequency on the network interface
port and output the in-bound data service signals on the data port.

13. The network gateway of claim 11, wherein the non-reciprocal signal
distribution circuit comprises: a circulator having three ports
electrically coupled to the network interface port, the content
transmission port, and the data port, respectively; and a feed-forward
interference cancellation circuit including a sampling input port
electrically coupled to the data port, and an cancellation output port
electrically coupled to the content transmission port.

14. The network gateway of claim 11, wherein the content signals includes
one or more of an analog format television signal and a digital format
television signal.

15. A method comprising: transmitting, over a conductor of a network, a
first signal modulated at a first frequency in a first direction; and
transmitting simultaneously with the first signal, over the conductor of
the network, a second signal modulated at the first frequency in a second
direction opposite the first direction.

16. The method of claim 15, further comprising: receiving the first
signal on a first port of a coupling circuit and outputting the first
signal on a second port of the coupling circuit to the conductor of the
network; receiving the second signal on the second port of the coupling
circuit from the conductor of the network and outputting the second
signal on a third port of the coupling circuit; and isolating the first
signal from the third port of the coupling circuit.

17. The method of claim 16, wherein the coupling circuit comprises: a
circulator; and a feed-forward interference cancellation circuit
configured to sample the first signals on the first port and output
cancellation signals on the third port.

18. The method of claim 15, wherein the first signal includes a data
service and the second signal includes a television service.

19. The method of claim 15, further comprising: providing a broadcast
television service and a data networking service to a user over the
network, wherein the first signal is a transmission of the television
service and the second signal is a transmission of the data networking
service.

20. The apparatus of claim 19, wherein the television service includes
one or more of an analog format television service and a digital format
television service.

Description:

BACKGROUND

[0001] Communication networks have evolved over time to provide multiple
mixed services to end users. Such networks, which once provided only
analog broadcast television, have been adapted to provide new services
such as digital television broadcasts, on-demand entertainment,
interactive television, and data networking. To support different groups
of users at different phases of network growth, networks have maintained
support for legacy services (e.g., analog television), while
simultaneously supporting new services (e.g., data networking). As new
services and users are added, such networks may become bandwidth-limited.

[0002] In order to expand services further, this disclosure identifies and
addresses a need to more efficiently utilize allocated frequency spectrum
within communication standards, and to develop new techniques for
utilizing unallocated frequency spectrum.

SUMMARY

[0003] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features or
essential features of the disclosure.

[0004] Methods and systems are disclosed for using a common frequency
spectrum for simultaneous upstream and downstream communications by
implementing directional diversity techniques in a wired medium.

[0005] In one embodiment, downstream video signals and upstream data
signals are transmitted over the same radio frequency spectrum, but in
opposite directions. Non-reciprocal coupling devices, such as
circulators, may be configured in the network to provide unidirectional
transmission of each signal or groups of signals to prevent interference
in other undesirable effects. In another embodiment, feed-forward
interference cancellation may be utilized to increase signal isolation of
upstream and downstream signals. These and other embodiments are further
discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 illustrates a network in which various embodiments may be
implemented.

[0007]FIG. 2 illustrates a network within a building in which various
embodiments may be implemented.

[0008] FIGS. 3A-3B illustrates a graphical depiction of an example
frequency spectrum allocation in a network according to various
embodiments.

[0009]FIG. 4 illustrates a network schematic diagram according to various
embodiments.

[0010]FIG. 5 illustrates graphical representations of signals carried
over the network of FIG. 4 according to various embodiments.

[0011]FIG. 6 illustrates a network schematic diagram and example signal
parameters according to various embodiments.

[0012]FIG. 7 illustrates graphical representations of signals carried
over the network of FIG. 6 according to various embodiments.

[0013]FIG. 8 illustrates a schematic block diagram of a computing
platform according to some embodiments.

[0014] FIG. 9 illustrates a network schematic diagram according to various
embodiments.

DETAILED DESCRIPTION

[0015]FIG. 1 illustrates a data access/distribution system 100, for
delivering data such as audio-visual programming to users over a
communication link. Networks in the system may incorporate fiber-optic
technology, wireless, co-axial cable or other technologies, or any
combination thereof and two-way communication in the network to expand
the network's capability. Such systems provide various services,
including data, standard and high definition digital television, data
networking and Internet connectivity, on-demand entertainment (e.g.
Video-On-Demand (VOD)), voice-over-Internet Protocol (VOIP), interactive
television, and other services.

[0016] The central location 101 operates to receive and process content
(e.g., audio, video, or other data), and distribute the content to users
(e.g., subscribers). The content may be received from a number of program
or content providers 102a-c, through various communication media such as
microwave and RF antennas, satellite links, direct-wired or wireless
connections, other communication links, and/or through recordable media,
for example. The central office may modulate the programs onto optical or
RF signals, and transmit the modulated signals over the network plant to
the users. The central office 101 may be a single facility, or may be
multiple facilities, which include a number of computer servers
interconnected through a local network, that operate together to perform
the receiving and distribution of content.

[0017] The networks in system 100 may include in one implementation a
number of fiber-optic cables that run from the central office facility
101 to optical distribution points 103A and 103B. While two optical
distribution points are shown, network 100 may include any number of
optical distribution points as required by the geographical areas and
distances served. The fiber-optic cables carry signals in digital form as
pulses of light reflected down the glass fiber-optic cable. The pulses of
light may be received and repeated by the optical distribution points
onto a number of additional fiber-optic cables to optical nodes 104A,
104B, 104C, and other optical nodes, which have not been illustrated for
convenience.

[0018] The optical nodes convert the pulses of light carried on the fiber
optic cable into RF signals having various analog and/or digital formats
(e.g., NTSC, ATSC, DVB-T, etc.), which are amplified and transmitted
through the coaxial cable portion of the network to serve neighborhoods
of users. These neighborhoods are illustrated as 107A-C, which consist of
one or more homes (e.g., 2000 homes) per optical node. System 100 may
employ networks that also, or alternately, include wired links, coaxial
cable, twisted shielded pair wire, additional fiber-optic cable, power
lines, etc., and associated components.

[0019] Within each neighborhood, the network may include, in one aspect, a
number of trunk and feeder lines 105A-F interconnected with RF amplifiers
106A-C, to individual coaxial drop lines to each home. The amplifiers
106A-C, optical nodes 104A-C, and optical distribution points 103A-B may
each have the capability to transmit and receive signals in both
directions, which enables the network to transmit signals, which
originate from users, back to the central office 101. The two-way
communication, combined with the high rate of data enabled by the fiber
optics, allow the network 100 to provide interactive audio-visual
services and data services.

[0020] As shown in FIG. 2, within each home, dwelling (e.g., multi-unit
dwelling) or facility connected to networks of system 100, an in-home
network 200 may connect one or more user devices such as customer premise
equipment (CPE) 202-207 to network 100 through a distribution network
201. Network 201 may include one or more RF couplers, amplifiers, filters
and splitter, isolators, circulators, etc.

[0021] In many cases, networks 100 and 200 may have to support legacy,
current, and emerging technologies simultaneously. For example, the CPEs
may include analog devices, such as analog televisions and set-top boxes
202, which receive and display analog broadcasted television programs. As
one example, the networks may carry National Television System Committee
(NTSC) analog television 6 MHz broadcast channels. In addition to analog
services, the networks may carry digital broadcast channels, which are
received by digital televisions 206, digital terminal adaptors
(DTAs)/set-top boxes 203, and digital video recorders (DVR) 204. The
networks may further carry digital communication and interactive
services, which may be accessed through devices such as cable
modems/embedded multimedia terminals (eMTA) 205, voice over IP (VOIP)
terminals 207, and other devices.

[0023] In FIG. 3A, a portion of the bandwidth (e.g., 54 MHz-855 MHz) may
be portioned into, for example, 6 MHz (or other width) channels, in which
signals from multiple different standards may be allocated. For example,
54-216 MHz may be allocated to National Television System Committee
(NTSC) analog television broadcast channels. The bandwidth from 54 MHz to
60 MHz may be allocated to channel 2 (i.e., EIA-2), 60 MHz to 66 MHz may
be allocated to channel 3 (i.e., EIA-3), etc. The bandwidth for
transmitting analog channels may be selected depending on the number of
analog channels and the analog standard applied. For example, the range
of 54-216 MHz may include 27 channels, each having a 6 MHz bandwidth. The
precise bandwidth and frequency limits of each channel may also be
selected according to different standards (e.g., EIA-542B, STD, HRC, IRC,
PAL, etc.), broadcasting geographical regions (e.g., North America,
Japan, Europe, etc.), tuning equipment, and other considerations.

[0024] Another portion of the bandwidth shown in FIG. 3A may be allocated
for digital television transmission. For example, 217-517 MHz may be
allocated to Advanced Television Systems Committee (ATSC) digital
television channels. Each ATSC channel may occupy a 6 MHz bandwidth
similar to the NTSC channels, and each ATSC channel may each include
multiple digital sub-channels. For example, the range of 217-223 MHZ may
carry digital channel 23 with three sub-channels (e.g., 23.1, 23.2, and
23.3). The bandwidth for carrying digital channels may be selected
depending on number of digital channels and the digital standard applied.
For example, the range of 217-517 MHz may include 50 digital channels.
The bandwidth and frequency limits of each digital channel may be
determined according to different digital television standards (e.g.,
ISDB ATSC, DVB, SMB, etc.), broadcasting geographical regions (e.g.,
North America, Japan, Europe, etc.), tuning equipment and other
considerations.

[0025] Another portion of the bandwidth shown in FIG. 3A may be allocated
for high-speed data transfer. For example, 5-42 MHZ may be allocated for
upstream data transfer and 518-855 MHz may be allocated for downstream
data transfer. In one aspect, the data transfers may conform to a
DOCSIS® service. The DOCSIS® downstream service may be
partitioned in two 6 MHz channels and the DOCSIS® upstream service
may be partitioned into 200 kHz, 3.2 MHz or 6.4 MHz channels. The channel
width and frequency limits may be tailored according to different
regional requirements, communication standards, and data requirements.
For example, in North America the data (e.g., DOCSIS) downstream channels
maybe 6 MHz wide, while in Europe the data (e.g., DOCSIS) downstream
channels maybe 8 MHz wide to coincide with respective analog and digital
transmission standards in each region.

[0026] The frequency spectrum shown in FIG. 3A may support other types of
data services. For example, Multimedia-Over-Cable (MOCA®) is one type
of service that allows devices (e.g., set top boxes) in a home network
(e.g., Network 200) to communicate and stream data between each other. In
FIG. 3A, the bandwidth from 860-1500 MHZ may be allocated for MoCA®
services.

[0027] The allocation of the frequency spectrum to the various standards
in FIG. 3A may be limited in two respects.

[0028] First, many of the services defined by the various standards (e.g.,
DOCSIS®, NTSC, ATSC, etc.) cannot share bandwidth with services of
other standards. For example, the DOCSIS® standards may permit
upstream communication in a frequency band of 5-85 MHZ, but for example,
the DOCSIS® upstream communications cannot overlap the NTSC
downstream broadcast channels from 54-85 MHZ. Likewise variations of the
NTSC standard may permit analog broadcast channels below 54 MHz, however,
these analog channels, cannot overlap the DOCSIS® upstream service.

[0029] In a second respect, full utilization of the network bandwidth
might not be achieved due to lack of standards defined for utilizing
unallocated bands of the spectrum. For example, while MOCA® may be
defined for frequencies up to 1500 MHZ, a network including optical fiber
coaxial cable may support communications signals up to 2000 MHz.

[0030]FIG. 3B illustrates a frequency spectrum allocation according to
various embodiments, which improve bandwidth utilization. In one aspect,
directional diversity techniques are utilized to simultaneously transmit
downstream television signals and upstream data signals over the same
radio frequency spectrum on a network, but in opposite directions.
Directional diversity refers to the distinction between two signals
transmitted on a common medium based on the signals traversing the common
medium in opposite or different directions. In one embodiment, in a
system employing DOCSIS® or other data standard, the data upstream
communication bandwidth may be expanded to a full frequency range of 5-85
MHz defined by the standard, which map overlap downstream NTSC analog
television channels in the range of 54-85 MHz. The upstream data signals
may be distinguished from the NTSC analog television signal based on
directional diversity.

[0031] Various aspects may include bi-directional data transmission in
unassigned frequency spectrum in a hybrid fiber-coaxial or other wired
network. For example, a frequency spectrum of 1500-2000 MHZ may not be
utilized by any standard, but may be within the physical transmission
capabilities of the network. Upstream communications 301 and downstream
communications 302 may be defined to simultaneously utilize this unused
frequency range, and may be distinguished using directional diversity
techniques.

[0032] In other variations, the frequency spectrum may be proportioned
differently. For example, the frequency spectrum may include more, less
or no bandwidth for analog television signals, digital television
signals, data downstream signals, DOCSIS® downstream signals and/or
MoCA® signals. Certain variations, for example, may include no analog
television channels. In such a case, the data (e.g., DOCSIS®)
upstream communications may overlap Digital television signals or data
(e.g., DOCSIS®) downstream signals assigned to frequency band of
54-85 MHz or in other frequency bands.

[0033]FIG. 4 illustrates a schematic of a network branch in networks 100
and 200, which may be utilized according to various embodiments to take
advantage of directional diversity. In FIG. 4, non-reciprocal coupling
devices, such as circulators, and/or feed forward interference
cancellation circuits may be configured in the network to provide
unidirectional transmission of each signal along a common network branch
to prevent interference.

[0034] In FIG. 4, network branch 400 simultaneously carries downstream
television or other data signals from a transmitter node 401 to a
receiver node 402 and upstream data signals from a transmitter node 403
to a receiver node 404 over a common transmission path 413. Transmitter
node 401 may be, for example, the central office 101 of FIG. 1 or an
intermediate node within FIGS. 1 and 2 (e.g., 103A-B, 104A-C, 106A-C,
201, etc.) transmitting analog television to an end device (e.g.,
television 206, set top box 204, etc.). Receiver node 402 may be an end
device within network 200 (e.g., television 206, set top box 204, etc.)
or may be an intermediate node receiving signals from upstream in the
network. While FIG. 4 illustrates the downstream signals to be television
signals, the downstream signals may include any type of content such as
audio, video, or other data, such as analog television, digital
television, and/or downstream DOCSIS® signals (or another
specification) as allocated in FIGS. 3A and 3B, or as allocated according
to other frequency plans.

[0035] Data transmitter node 403 may be, for example, a cable modem 205, a
VOIP terminal 207, an optical node, or other end devices, or an
intermediate node such as 103A-B, 104A-C, 106A-C, 201, etc. Data receiver
node 404 may be, for example, central office 101 or an intermediate node,
which is upstream from transmitter node 403. Upstream data signals may
include, in one embodiment, DOCSIS® signals in a frequency range of
5-85 MHZ, and/or other upstream data signals according to other standards
and other frequency bands.

[0036] In various embodiments transmitter node 401 and receiver node 404
may be separate devices, or may be a common device. Likewise, transmitter
node 403 and receiver node 402 may be separate devices or may be a common
device (e.g., set top box 203).

[0038] In FIG. 4, non-reciprocal coupling devices, such as circulators 405
and 406 may be used to isolate upstream and downstream signals
transmitted across path 413. The non-reciprocal coupling devices 405 and
406 are multi-port devices, which permit transmission of signals received
on a first port to an adjacent port in rotation but isolate the signals
received on the first port from other ports on the circulator. In certain
embodiments, non-reciprocal coupling devices 405 and 406 may pass signals
from ports 1 to 2, 2 to 3, and 3 to 1 with little insertion loss (e.g.,
clockwise), but provide high isolation for signals from ports 1 to 3, 3
to 2, and 2 to 1 (e.g., counterclockwise). Here an adjacent port in
rotation (e.g., clockwise or counterclockwise) refers to how the port may
be schematically illustrated, and does not refer to the geometric
position of the port on the actual physical device relative to other
ports on the device. The rotational directions for passing or isolating
signals are chosen for convenience only. Other directional conventions
may also be used to describe the devices signal behavior.

[0039] In various embodiments, the insertion loss may be typically 0.2 to
0.4 dB (for a passive device) in the clockwise direction (as
illustrated), and 30-60 dB of isolation in the counter-clockwise
direction over the operating frequency range of the network (e.g., 5 MHz
to 2 GHz). The exact insertion loss and isolation values depend on the
application and design of the circulator device. Such devices may include
coaxial, waveguide, and/or optical type circulators and may include
passive materials (e.g., ferrites) and/or active circuits for
conditioning the signals.

[0040] In FIG. 4, a signal transmitted from transmitter 401 will pass
through device 405, path 413, and device 406 to receiver 402 with a
signal loss predominantly resulting from the line loss of path 413. In
contrast, the signal transmitted from transmitter 401 will be isolated by
at least 40 dB from data receiver node 404 due to the isolation from
device 405 in the counter-clockwise direction. In a similar fashion,
signals transmitted from transmitter node 403 will pass to receiver node
404 with signal loss predominantly due to only the line loss of path 413,
while at the same time being isolated by at least 30 dB from node 402.

[0041] Using feed forward interference cancellation techniques, the
transmitted signals may be further isolated from the unintended
receivers. In one embodiment, signals transmitted from node 401 are
sampled at port 1 of device 405 by interference cancellation circuit 407.
The sampled signals are adjusted in gain, phase, and delay by circuit
407, summed at node 409 with signals from port 3 of device 405, and
output to receiver node 404. Interference cancellation circuit 407
adjusts the sampled signals such that they cancel signals that propagate
through device 405 from port 1 to port 3. In various embodiments, this
feed forward interference cancellation may provide an additional 40 dB of
isolation. In a similar fashion, circuits 408 and 410 may provide an
additional 30 dB of isolation at node 402 from signals transmitted from
node 403.

[0042] Devices 407 through 409 may include a combination of the analog and
digital electronics. For example, the sampling circuit 407 may consist of
discrete inductors and capacitors or parallel microstrip lines on printed
circuit board forming a directional coupler, or other equivalent device.
The addition circuit shown in the figure as block 409 may also be a
printed circuit, lumped element directional coupler, or other equivalent
device. Circuits 407 and 409 cancel the interference by adding a signal
equal in amplitude and time delay, and 180 degrees out of phase with the
interference from 401. In one embodiment, circuit 407 may comprise gain
adjust circuitry (e.g., a PIN diode attenuator that includes devices
whose resistance changes with current), phase adjust circuitry (e.g.,
varactor diodes whose capacitance changes with voltage), and time delay
circuitry (e.g., a delay line such as a meandering transmission line
formed with a high dielectric substrate in order to get the maximum time
delay in the minimum amount of space). The circuitry in 407 may create a
larger time delay than the path though the circulator 405 ports 1 to 3.
In some implementations, to adjust for this larger time delay, a time
delay circuit is placed between element 405 and 409 in addition to, or
instead of the time delay circuit in 407.

[0043] In other embodiments, element 407 can alternatively or additionally
be implemented with an analog to digital converter to sample the signal
at port 1 of 405, a digital signal processor to perform gain, time delay,
and phase adjustment on the sampled converted signal, and a digital to
analog converter and amplifier to output the signal to 409. In this case,
the gain, phase and time delay circuits are mathematical representations
of the above analog circuits, which are operated on by the digital signal
processor.

[0044]FIG. 5 illustrates example signal levels transmitted between nodes
in the embodiment illustrated in FIG. 4. The graph labeled TV TX
illustrates an example NTSC analog television signal transmitted from
node 401. The NTSC television signal bandwidth may be 6 MHZ (e.g., 54-60
MHz for channel 2) and may include visual, color, and aural signals
transmitted at levels of +40 dBmV. The graph labeled CM TX illustrates an
example broadband data signal transmitted from node 403 over the same 6
MHz band as the signal transmitted from node 401. In one embodiment, the
data signal may be transmitted at a level of +20 dBmV.

[0045] The graph labeled TV RX illustrates the transmitted signals
received at receiver node 402. In the graph the NTSC television signals
transmitted from 401 are received at node 402 attenuated by 30 dB. The
attenuation is substantially due to the line loss of path 413 (assuming
negligible loss through devices 405 and 406). Also illustrated in this
graph are the data transmission signals from node 403. As illustrated,
these signals are attenuated by a combined 60 dB due to the isolation
provided by device 406 and by the feed forward interference cancellation
circuit 408. Assuming that node 402 is designed to receive the NTSC
television signals, devices 406 and 408 provide a 50 dB signal to noise
ratio of the television signals over the data signals, which are treated
as noise. Also illustrated in the graph is the -53 dBmV thermal noise
floor, which assumes a 75 ohm impedance, room temperature, 6 MHz
bandwidth, and 4 dB noise FIG. of receiver node 402.

[0046] The graph labeled CM RX illustrates the transmitted signals
received at receiver node 404. In the graph the data signals transmitted
from node 403 are received at node 404 attenuated by 30 dB. This
attenuation is substantially due to the line loss of paths 413 (assuming
negligible lost through devices 405 in 406). Also illustrated in this
graph are the data transmission signals from node 401. As illustrated,
the signals are attenuated by a combined 80 dB due to the isolation
provided by devices 405 and 407. Assuming that node 404 is designed to
receive the data signals from node 403, devices 405 and 407 provide a 30
dB signal to noise ratio of the data signals over the television signals,
which are treated as noise. Also illustrated in the graph is the -53 dBmV
thermal noise floor, which assumes a 75 ohm impedance, room temperature,
6 MHz bandwidth, and 4 dB noise FIG. of receiver node 404.

[0047] In various embodiments, the television signals transmitted from
node 401 may be, for example, NTSC analog television signals, and the
data signals transmitted from node 403 may be upstream data signals, such
as DOCSIS® data signals, both in the frequency range of 54-85 MHZ as
illustrated in FIG. 3B.

[0048]FIG. 6 illustrates a schematic of another embodiment of a network
branch 600 in networks 100 and 200, for example, which may be utilized
according to various embodiments to take advantage of directional
division duplexing. Like the network branch 400 in FIG. 4, network branch
600 that may include non-reciprocal coupling devices, such as circulators
to provide unidirectional transmission to prevent interference of
upstream and downstream signals along branch 600. The network branch 600
may, for example, carry the upstream signals 301 and downstream signals
302 illustrated in FIG. 3B. These signals may occupy the frequency range
of 1500-2000 MHz, which might not be occupied by other standards (e.g.,
MoCA®, DOCSIS®, etc.) in communication networks 100 and 200.

[0049] In FIG. 6, network branch 600 may simultaneously carry downstream
data signals 301 from a transmitter node 601 to a data receiver node 602
and upstream data signals 302 from a transmitter node 603 to a receiver
node 604 over a common transmission path 607. Transmitter node 601 may
be, for example, located at the central office 101 of FIG. 1 or an
intermediate node within FIGS. 1 and 2 (e.g., 103A-B, 104A-C, 106A-C,
201, etc.) transmitting high speed data to an end device (e.g., 202-207).
Receiver node 602 may be an end device within network 200 (e.g.,
202-207), or may be an intermediate node receiving signals from upstream
in the network.

[0051] In various embodiments, data transmitter node 603 may be a cable
modem 205, a VOIP terminal 207, other end devices, or an intermediate
node such as 103A-B, 104A-C, 106A-C, 201, etc. Data receiver node 604 may
be, for example, central office 101 or an intermediate node, which is
upstream from transmitter node 603. In various embodiments transmitter
node 601 and receiver node 604 may be separate devices, or may be a
common device. Likewise, transmitter node 603 and receiver node 602 may
be separate devices or may be a common device (e.g., cable modem 205).

[0052] In FIG. 6, non-reciprocal coupling devices, such as circulators 605
and 606 may be used to isolate upstream and downstream signals
transmitted across path 607. Like devices 405 and 406 in FIG. 4, the
non-reciprocal coupling devices 605 and 606 are multi-port devices, which
permit transmission of signals received on a first port to an adjacent
port in rotation but isolate the signals received on the first port from
other ports on the circulator. Such devices may include coaxial,
waveguide, and/or optical type circulators and may include passive
materials (e.g., ferrites) and/or active circuits for conditioning the
signals. In certain embodiments, non-reciprocal coupling devices 605 and
606 may pass signals from ports 1 to 2, 2 to 3, and 3 to 1 with little
insertion loss, but provide high isolation for signals from ports 1 to 3,
3 to 2, and 2 to 1.

[0053] In the circuit illustrated in FIG. 6, a signal transmitted at a
level T1 from transmitter 601 will pass through device 605, path 607, and
device 606 to receiver 602 with a signal loss predominantly resulting
from the line loss L of path 607. In contrast, the signal transmitted
from transmitter 601 will be isolated from receiver 604 by device 605,
which provides isolation I1 in the counter-clockwise direction. In a
similar fashion, signals transmitted at a level T2 from transmitter node
603 will pass to receiver node 604 with signal loss predominantly due to
only the line loss L of path 603, while at the same time being isolated
from receiver 602 by device 606, which provides isolation I2 in the
counter-clockwise direction.

[0054] Signal levels at the receiver 602 are illustrated in the box
labeled Receiver 1. At receiver device 602, the signal level R1 of the
data transmitted from transmitter device 601 may be the transmitter level
T1 minus the cable line loss L (R1=T1-L, in dB). The noise level N1 at
receiver 602 caused by the data transmitted from transmitter 603 may be
the transmitter level T2 minus the isolation I2 provided by device 606
(N1=T2-I2, in dB). Assuming other noise at receiver 602 (e.g., thermal
noise) is less than the noise caused by the signals transmitted from
transmitter device 603, the signal-to-noise ratio Q1 at receiver 602 may
be given by receive level R2 minus the noise level N1 (in dB). As shown
in FIG. 6, when the transmitter levels T1 and T2 are equal, the
signal-to-noise level Q1 can be determined as the isolation from device
606 minus the cable line loss L (Q1=I2-L).

[0055] The signal level R2 of the signal transmitted from transmitter 603,
the noise N2 caused by the signal transmitted from transmitter 601, and
the signal-to-noise ratio Q2 at the receiver 604 are illustrated in the
box labeled Receiver 2, and are similar to those for receiver 602.

[0056] At the bottom of FIG. 6, characteristics of one embodiment are
illustrated. It will be appreciated that these characteristics are
illustrative only, and that other embodiments of network branch 600 may
have other characteristics that depend on the specific components, data
transmissions, and requirements of the other embodiments.

[0057] In the embodiment having the illustrative characteristics at the
bottom of FIG. 6, the upstream signals 301 and downstream signals 302 may
be modulated in QPSK format, which has a spectral efficiency of 2 bits
per second per Hertz of bandwidth. Given a bandwidth of 500 MHz (e.g.,
1500 MHz-2000 MHz), the maximum data rate of each upstream and downstream
data link may be 1 Gigabit per second (Gbps). The system may also have a
12 dB signal-to-noise ratio requirement to achieve a desired bit error
rate.

[0058] Transmission levels from transmitters 601 and 603 (T1 and T2) may
be, for example, +35 dBmV and the cable loss may be 40 dB. Such a cable
loss may, for example be characteristic of approximately 470 feet of RG-6
coaxial cable having an average loss of 8.5 dB per foot at 2 GHz.
Isolation I1 and I2 for the circulators may be 60 dB.

[0059] In the embodiment, thermal noise power is approximated to be -39
dBmV for a 75 ohm cable at room temperature, and receivers 602 and 604
may have approximately a 4 dB noise figure. This results in an
approximate thermal noise floor of -35 dBmV.

[0060]FIG. 7 illustrates signal levels in the embodiment of FIG. 6 given
the above illustrative characteristics. The graphs labeled Transmitter
601 and Transmitter 603 illustrate example data transmission signals from
nodes 601 and 603 respectively over the same frequency band of 1.5-2.0
GHz. The signals may be the signals 302 and 301 respectively illustrated
in FIG. 3B. In the embodiment described in FIG. 6, the signals may be
broadband signals transmitted at a +35 dBmV level.

[0061] The graphs labeled Receiver 602 and Receiver 604 illustrate the
transmitted signals received at receiver nodes 602 and 604 respectively.
In the Receiver 602 graph the data signal transmitted from 601 (i.e.,
signal level T1) is received at node 602 attenuated by 40 dB (i.e.,
signal level R1), and the data signal transmitted from 603 is received at
node 602 attenuated by 60 dB (i.e., noise level N1). The attenuation of
the 601 signal at 602 is substantially due to the line loss of path 607
(assuming negligible loss through devices 605 and 606), and the
attenuation of the 603 signal at receiver 602 is substantially due to the
isolation provided by device 606 in the counter-clockwise direction.

[0062] Similarly, in the Receiver 604 graph the data signal transmitted
from 603 (i.e., signal level T2) is received at node 604 attenuated by 40
dB (i.e., signal level R2), and the data signal transmitted from 601 is
received at node 604 attenuated by 60 dB (i.e., noise level N2). The
attenuation of the 603 signal at 604 is substantially due to the line
loss of path 607 (assuming negligible loss through devices 605 and 606),
and the attenuation of the 601 signal at receiver 604 is substantially
due to the isolation provided by device 605 in the counter-clockwise
direction.

[0063] The Receiver 602 and Receiver 604 graphs illustrate the thermal
noise floor of -35 dBmV, which is below the N1 and N2 noise levels due to
the signals transmitted from 603 and 601 respectively. As such, the
signal-to-noise ratio may be determined as the difference (in dB) between
R1 and N1, and between R2 and N2. As illustrated, the signal-to-noise
ratio is 20 dB for the illustrative characteristics in FIG. 6. This
provides an 8 dB margin over the required 12 dB signal-to-noise ratio of
the system.

[0064]FIG. 8 is a block diagram of equipment 800 in which the various
disclosed transmitter devices, receiver devices, gateways, servers, and
other described embodiments may be implemented. For example, devices 101,
201-207, 401-404, and 601-604, may include various portions of equipment
800 for transmitting and receiving data.

[0065] A main processor 801 is configured to execute instructions, and to
control operation of other components of equipment 800. Processor 801 may
be implemented with any of numerous types of devices, including but not
limited to, one or more general-purpose microprocessors, one or more
application specific integrated circuits, one or more field programmable
gate arrays, and combinations thereof. In at least some embodiments,
processor 801 carries out operations described herein according to
machine-readable instructions (e.g. software, firmware, etc.) stored in
memory 802 and 803 and/or stored as hardwired logic gates within
processor 801. Processor 801 may communicate with and control memory 802
and 803 and other components within 800 over one or more buses.

[0066] Main processor 801 may communicate with networks (e.g., networks
100 and 200) or other devices across one or more RF, microwave, and or
optical interfaces 804 that may include a coaxial cable connector (or
other type of connector) 805, a signal conditioning circuit 809 (e.g.,
filter), a diplex filter 806, a tuner 807 (e.g., wideband, narrowband,
television, FM, QPSK, QAM, etc.), upstream communication amplifier 808,
and one or more standard specific interfaces 812 (e.g., a MOCA®
interface, a DOCSIS® interface, etc.). Main processor 801 may also
communicate with other devices through additional interfaces, such as a
USB interface 810, Ethernet interface 815, wireless interfaces 813 (e.g.,
Bluetooth, 802.11, etc.), etc. A power supply 816 and/or battery backup
817 may provide electrical power. User input to equipment 800 may be
provided over one of the aforementioned interfaces (e.g., 804, 810, 813,
815, etc.), or via a separate collection of buttons, infrared ports, or
other controls in a console 821. Equipment 800 may include one or more
output devices, such as a display 823 (or an external television), and
may include one or more output device controllers 822, such as a video
processor.

[0067] Memory 802 and 803 may include volatile and non-volatile memory and
can include any of various types of tangible machine-readable storage
medium, including one or more of the following types of storage devices:
read only memory (ROM) modules, random access memory (RAM) modules,
magnetic tape, magnetic discs (e.g., a fixed hard disk drive or a
removable floppy disk), optical disk (e.g., a CD-ROM disc, a CD-RW disc,
a DVD disc), flash memory, and EEPROM memory. As used herein (including
the claims), a tangible machine-readable storage medium is a physical
structure that can be touched by a human. A signal would not by itself
constitute a tangible machine-readable storage medium, although other
embodiments may include signals or other ephemeral versions of
instructions executable by one or more processors to carry out one or
more of the operations described herein.

[0068] While some embodiments describe a single communication branch of a
network, other embodiments include networks having multiple branches
utilizing the directional disparity techniques and architectures
described herein in one or more of the branches. FIG. 9 shows an
embodiment including a point-to-multipoint downstream and
multipoint-to-point upstream configuration using directional diversity.
The architecture of FIG. 9 is similar to FIG. 1, with the components of
FIG. 4 and/or FIG. 6 added. The architecture in FIG. 9 may include an
optical distribution point 901, which may be the same or similar to the
optical distribution points 103A and 103B shown in FIG. 1. Distribution
point 901 may include an optical transmitter (Tx) for downstream
transmission and an optical receiver (Rx) for upstream reception over
optical cables to and from optical fiber node 902.

[0069] Node 902 may be the same or similar to nodes 104A-C illustrated in
FIG. 1. Node 902 may include an optical receiver that receives an optical
signal over the optical cable from 901, and converts the signal into an
RF signal amplified through a downstream amplifier. The
downstream-amplified RF signal may then be filtered through a bandpass
filter having a pass band in the range of the downstream signals. For
example, the pass band may be 54-855 MHz to pass the NTSC TV Channels,
Digital TV channels and data (e.g., DOCSIS®) downstream signals
illustrated in FIG. 3B. In other embodiments, the pass band may have a
different range depending on the intended downstream signals to pass.

[0070] Node 902 may also include an optical transmitter that may receive
an amplified RF signal from an upstream amplifier, and may convert the
amplified RF signal to an optical signal that is transmitted upstream
over the optical cable to 901. The amplifier may receive upstream signals
that have been filtered through a band pass filter having a pass band in
the range of the intended upstream signals. For example, the pass band
may be 5-85 MHz to pass the data (e.g., DOCSIS®) upstream signals
illustrated in FIG. 3B. In other embodiments, the pass band may have a
different range depending on the intended upstream signals to pass. The
RF upstream and downstream signals may be coupled through a circulator to
coaxial feeder line 903 for connection to households. The circulator may
be the same or similar to the circulator 405 and 605 shown in FIG. 4 and
FIG. 6, respectively.

[0071] Along the coaxial feeder path 903, one or more multi-drop hubs 905
may be included for connecting coaxial drop lines to individual end
devices. Devices 905 may include directional couplers, splitter devices,
etc., arranged to isolate signals from one home drop line to another home
drop line and from downstream signals (e.g., regardless of direction).

[0072] Feeder path 903 may further include one or more bidirectional
amplifiers 904. The amplifier may include the same or similar RF
components as 902 (e.g., amplifier, filter, directional coupler, feed
forward circuit, etc.) configured in a back-to-back arrangement. In 904,
a downstream-connected directional coupler circuit 907 and an
upstream-connected directional coupler circuit 908 separate upstream and
downstream signals. The upstream signal ports of 907 and 908 are
connected together through a set of one or more amplifiers and filters,
and the downstream signals ports of 907 and 908 are connected together
through a different set of one or more amplifiers and filters. In some
embodiments, the pass band for the downstream signals may be in the range
54-855 MHZ to pass the NTSC TV Channels, Digital TV channels and
downstream data signals illustrated in FIG. 3B, and the pass band for the
upstream signals may be 5-85 MHz to pass the data upstream signals
illustrated in FIG. 3B. In other embodiments, the pass bands may have
different ranges depending on the intended downstream and upstream
signals.

[0073] Block 906 illustrates one configuration in a home or other facility
at the end of a drop line for connection to the network. The circuit may
be the same or similar to the RF circuits in 902. The downstream
separated signal may connect to an analog or digital TV and/or a cable
modem receiver. The upstream separated signal may connect to a cable
modem transmitter.

[0074] While only a single circulator circuit for each network connection
is illustrated in 902, 904, and 906 to provide separation of upstream and
downstream signals, 902, 904, and 906 may include circuits such as 407
and 409 illustrated in FIG. 4 to provide further isolation using feed
forward cancellation. Also, while 902, 904, and 906 show one band pass
filter and amplifier for each path; 902, 904, and 906 may include
multiple band pass filters and amplifiers. Further, the band pass filters
may be located on either or both sides of each amplifier.

[0075] The foregoing description of embodiments has been presented for
purposes of illustration and description. The foregoing description is
not intended to be exhaustive or to limit embodiments to the precise form
disclosed, and modifications and variations are possible in light of the
above teachings or may be acquired from practice of various embodiments.
The embodiments discussed herein were chosen and described in order to
explain the principles and the nature of various embodiments and their
practical application to enable one skilled in the art to utilize the
present invention in various embodiments and with various modifications
as are suited to the particular use contemplated. All embodiments need
not necessarily achieve all objects or advantages identified above. All
permutations of various features described herein are within the scope of
the invention.

[0076] For example, although some embodiments are described in the context
of a hybrid fiber-coaxial data distribution network, other embodiments
include different types of networks. Other networks including
coaxial-cable only networks, fiber-optic only networks, POTS networks,
DSL networks, power line networks, other wired networks, and combinations
thereof. The networks of various embodiments may also utilize various
different types of physical communication media (e.g., twisted pair
conductors, coaxial cable, fiber-optic cable, power line wiring, etc.).